Liquid sealed rotary compressors have been in common use for many years. Such compressors are simple in design, are readily manufactured, and are well suited for continuous duty applications.
Because these devices usually incorporate a high speed rotor having numerous vanes, and inasmuch as they operate at constant speed, it is typical in such units in such devices produce a significant high frequency tone which is unacceptable or undesirable in many applications. Historically, uses of these devices have employed reactive type, tuned silencers on either the input conduit or output conduit, or both, to reduce the noise level. The need for silencers is balanced against the cost and the available space permitted for such devices. In addition, the silencers frequently employed are much less than optimal, inasmuch as they are not specifically designed to filter the frequencies produced by the specific compressor configuration while minimizing the pressure drop involved.
Accordingly, a primary object of the present invention is to provide unique silencers as part of a port and manifold assembly, which is integrated with a compressor device, so as to enable optimal silencing precisely because such silencers are specifically designed to filter the frequencies produced by the specific compressor configuration.
In realizing the primary object stated above, the primary feature of the present invention resides in the provision of configuring the intake and output manifold geometries in such a fashion as to create a pair of separate broad banded reactive filters integral to both the internal input manifold and the internal output manifold.
An ancillary objective is to achieve this configuration within the existing volume envelope typical of known compressors not so equipped. Such volume envelope of currently designed compressors is a cylindrical shape 17" long and 7" in diameter. Any product designed to serve this market must not exceed these dimensions.
A further object is to produce a more complete noise reduction scheme by locating the reactor silencers directly at the source of the noise.
Yet another object is to achieve a design which is more cost effective than is the addition of external silencers.
Other objects are to achieve a design which eliminates the need for additional space to accommodate external silencers; to produce a compressor which is inherently quiet and thus is more attractive in the marketplace; and, further, to produce a compressor so equipped and configured that it may be installed and operated effectively in most applications in which a conventional compressor of similar performance levels has been deployed.
The inventor's Assignee, Dielectric Communications of Raymond, Maine, a division of General Signal Corp., has been manufacturing a line of water sealed air compressors since the mid sixties. These compressors are used almost exclusively by the telephone industry to produce compressed air at pressures ranging up to approximately 30 PSIG. This compressed air is dried by special dryer systems, and is then introduced into telephone cables under pressure to prevent the intrusion of water into those cables. The compressors are typically packaged as an internal component in a compressor-dehydrator unit also manufactured by Dielectric.
The above noted compressor-dehydrators are frequently located in structures which are also the workplace of telephone company employees. Often several compressors will be operating simultaneously (for example, in one office in Manhattan there are thirty such compressors in one room), such that the deleterious noise effects are substantial.
It should be noted that the compressors common to this specific market range in sizes up to 5 hp, and they are always mounted directly to their associated motor and produce air at flow rates up to 25 SCFM at 25 PSIG. At present, none of the manufacturers supplying compressors of this general specification have envisioned or employed reactor silencers internal to the compressor structure. Accordingly, it is to this market that the present invention is directed and it will be apparent that such a quiet compressor could very likely become the industry standard replacing all other devices of like purpose in competitive compressor-dehydrators.